EP0735670A2 - Circuit pour détecter le niveau de puissance d'émission à caractéristique améliorée - Google Patents

Circuit pour détecter le niveau de puissance d'émission à caractéristique améliorée Download PDF

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Publication number
EP0735670A2
EP0735670A2 EP96301903A EP96301903A EP0735670A2 EP 0735670 A2 EP0735670 A2 EP 0735670A2 EP 96301903 A EP96301903 A EP 96301903A EP 96301903 A EP96301903 A EP 96301903A EP 0735670 A2 EP0735670 A2 EP 0735670A2
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EP
European Patent Office
Prior art keywords
signal
circuit
output
amplifier
port
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96301903A
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German (de)
English (en)
Other versions
EP0735670A3 (fr
Inventor
Leonid Strakovsky
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
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AT&T Corp
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Filing date
Publication date
Application filed by AT&T Corp filed Critical AT&T Corp
Publication of EP0735670A2 publication Critical patent/EP0735670A2/fr
Publication of EP0735670A3 publication Critical patent/EP0735670A3/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers
    • H03G3/3042—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers

Definitions

  • the present invention relates to control circuits for RF signal power amplifiers.
  • the basic operation and structure of wireless communication systems are well known in the art. Subscriber accommodation capacity is typically maximized by maintaining the RF transmission signal output power at a sufficiently low level, within each zone, to permit simultaneous usage of the same radio frequencies in nearby zones.
  • the transmitting power of the radio communication system is generally maintained at one of a plurality of prescribed levels by a transmission signal output control system.
  • the transmission signal output control system includes a detection circuit for detecting the power level of the transmission signal output by an RF power amplifier and a circuit responsive to the output of the detection circuit for controlling the gain of the RF power amplifier.
  • radiotelephones employ a feedback circuit to control the output of the power amplifier.
  • a portion of the RF output energy is applied to the detection circuit, which circuit provides a power level signal corresponding to the output power level.
  • the power level signal is compared to a reference signal in order to generate a control signal that is used to vary the amplifier's output power and cause the difference between the reference signal and the power signal level signal to be minimized.
  • FIG. 1 An RF transmission signal is amplified in an RF amplifier circuit 10 in the final stage and is then supplied through the input and output ports of a four-terminal, transmission line coupler 12 to an antenna output circuit 14.
  • the amplified RF transmission signal output by amplifier circuit 10 is supplied not only to the antenna circuit 14, but also to detector circuit 16 for detection in a conventional manner.
  • the coupler 12 is configured to divert approximately 3-5 % of the power output by amplifier circuit 10 to detector circuit 16.
  • the detector diode D1 of detector circuit 16 is connected to the couple terminal "C" of coupler 12 and thus, to the output side of the RF amplifier circuit 10.
  • the voltage at the anode of diode D1 is marginally forward biased by means of a biasing circuit 24 that includes a resistor R2, a diode D2, and a resistor R3.
  • a resistor R1 is coupled to the load terminal "L" of coupler 12.
  • the value of resistor R1 is generally selected to match the characteristic impedance of the circuit and may be, for example, on the order of 50 ohms. Due to the match termination, the load termination behaves as if it is of infinite length (no reflection) so that all power supplied to resistor R1 is absorbed and converted to heat.
  • the half-wave rectified detection signal is supplied to an output level control circuit 18 via a buffer amplifying circuit 20.
  • the output level control circuit 18 compares the output of the buffer amplifier circuit 20 with a variable level reference signal supplied from a reference level generation circuit 22, and controls the amplification of the RF amplifier circuit 10 so that antenna circuit 14 is supplied with an RF signal of the desired output level.
  • the dynamic range of the detector circuit is the range of coupled transmitted RF signal power levels at the power detector's input for which the power detector's output signal is usable.
  • the dynamic range of the power detector circuit is related to the power level of the coupled transmitted RF signal. Since the coupler has a fixed coupling coefficient, the fraction of the transmitted output RF signal supplied to the couple terminal of RF coupler 12 remains essentially constant regardless of amplitude. At high transmitter power levels, RF couplers couple a large amount of signal power for detection by the power detector, and a significant portion of the coupled transmitted RF signal is lost.
  • the current drain of the transmitter is increased to overcome the loss of power at high power levels, thereby reducing the transmitter's efficiency.
  • RF couplers provide a low amount of signal power level for detection by the detector circuit.
  • a substantial amount of the diverted signal power is dissipated by the resistor R1.
  • the circuit of FIG. 1 is unable to detect transmission signals that are below a certain amplitude threshold, which threshold may typically be on the order of 2 to 3 mW or even larger.
  • a radio frequency (RF) circuit includes an RF signal generating device for generating an RF output signal.
  • the first port of a four-port RF signal coupling device is coupled to the RF signal generating device, which device may be configured, for example, as an RF amplifier.
  • a detection circuit is coupled to the third port for obtaining a measurement of the amplitude of the RF output signal and an impedance termination having an impedance value different from the characteristic impedance is coupled to fourth port so that the third port receives a portion of signal energy delivered by said RF signal generating device and a portion of signal energy reflected from said fourth port
  • the impedance termination has a non-linear impedance value which varies with the amplitude of the output power signal.
  • this is achieved by an impedance inverter in series with a diode.
  • the diode itself approximates an open circuit.
  • the combination of the diode and impedance inverter thus behaves as a short circuit so that the signal reflected by the diode back to the detector circuit is in phase with the incident signal.
  • the precise number of reflections being governed by the loss characteristics of the circuit, i.e. the Q-factor, the signal incident on the diode may be reflected and added many times.
  • the transmit level detection circuit of the present invention thus requires substantially less power than conventional circuits, so that only 1%-2% or less of the output of the amplifier need be diverted for reliable operation.
  • the non-linear behavior of the diode initially causes slight clipping of the signal.
  • clipping does not materially affect the level of signal power available at the power detector circuit's input until much higher signal levels are achieved.
  • the combination of the diode and impedance inverter is at the same time configured to approach an open circuit condition as the signal incident on the diode approaches a given upper amplitude threshold.
  • clipping of the signal by the diode increases, causing the impedance of the diode to decrease.
  • a transmit power level detection circuit constructed in accordance with the present invention has a substantially enhanced dynamic range and thus avoids the deficiencies associated with conventional detection circuits.
  • the present invention provides gain at lower transmit power levels and, optionally, attenuation at higher transmit power levels.
  • the present invention allows substantially weaker signals, on the order of 0.5mW or less in amplitude, to be detected, so that a significantly smaller portion of the RF power amplifier output may be diverted to the detector circuit.
  • the detector circuit of the present invention can substantially lengthen the operating cycle time or allow a smaller battery to be used to obtain the same operating cycle time.
  • the impedance termination is configured as a short circuit or shunt path to ground so that the gain is always at a maximum, regardless of the amplitude of the transmitted RF signal.
  • FIG. 2 shows a block diagram of a communication unit embodying the present invention.
  • Communications units are generally well,known in the art and a detailed description of the same is not believed necessary for an understanding of the present invention. It suffices to say that RF signals generated in a conventional manner are supplied to a radio frequency (RF) power amplifier 10, where they are amplified to a desired RF power level, which level may be one of a plurality of predetermined power levels.
  • RF radio frequency
  • an RF coupler as coupler 12 generally comprises a primary transmission element (not shown) which interconnects the input and output terminals I and O, and a secondary coupling element (not shown) which interconnects the couple and load terminals C and L.
  • the primary transmission element thus receives at its input terminal an RF input and delivers an RF output at its output terminal.
  • the secondary coupling element couples a portion of the RF signal to produce a coupled RF output signal.
  • the coupled RF signal is output at terminal C of coupler 12 to power detector circuit 16, and is a reduced power level version of the input signal supplied to input terminal.
  • the relationship between the power levels of the signals output at terminals O and C is the coupling factor of RF coupler 12.
  • the coupling factor is selected large enough to provide enough coupled RF signal for proper operation of the detector circuit 16 at the lowest of the plurality of power levels at which the transmission unit operates.
  • the amount of gain provided by the present invention at the lowest RF power levels ensures that it is not necessary to select a coupling factor which impacts the efficiency of the transmission unit at higher power levels. That is, the selected coupling factor is low enough to avoid coupling off large amounts of power from the primary transmission element when the transmission unit is operating at the higher of the plurality of power levels.
  • the primary transmission element and first coupling element of RF coupler 12 can be formed from transmission lines in close proximity such as stripline or microstrip, or from any other transmission means allowing directive coupling, for exaniple, aperture coupled waveguides.
  • the coupling constant is selected as desired by changing the physical construction of the primary and coupling elements. For the case of stripline or microstrip couplers, varying the distance between transmission lines, the length over which the lines are in close proximity, or the dielectric constant of the substrate will produce the selected coupling constant.
  • the load resistor R1 of FIG. 1 has been replaced by an impedance inverter 30 in series with a diode D3.
  • the diode D3 is, for example, a Shottky barrier type diode, while the impedance inverter may be configured as a one-quarter wavelength transmission line or resonator.
  • An impedance inverting transmission line as such has first and second ends. The value of an impedance at the first end, appears at the second end, to be substantially equal to the mathematical inverse of the value at the first end, and vice versa.
  • the first end impedance is considered to be zero ohms.
  • the second end impedance will therefore be very high, or near infinity, appearing to be an open circuit.
  • the second end impedance will be near zero and may be considered to define a short circuit condition.
  • Diode D3 acts as a controlled resistance. As the transmitted signal approaches a lower amplitude threshold, say on the order of one-hundredth of a milliwatt, the diode D3 itself approximates an open circuit. The combination of diode D3 and impedance inverter 30 therefore behaves as a short circuit so that the signal reflected by diode D3 back to the detector circuit 16 is in phase with the incident signal. With the precise number of reflections being governed by the loss characteristics of the circuit, i.e. the Q-factor, the signal incident on diode D3 may be reflected and added many times at the couple port C of the RF coupler 12.
  • the gain increases correspondingly such that a maximum gain on the order of 50 or more may be easily achieved. A substantial increase in gain is thus achieved precisely when it is needed, so that the amplitude threshold for detection is substantially reduced in comparison to conventional power level detection schemes.
  • the amplitude of the RF signal increases beyond the low amplitude threshold; the non-linear behavior of diode D3 initially causes slight clipping of the signal. Such clipping does not materially affect the level of signal power available at the power detector circuit's input until much higher signal levels are achieved, as will now be explained.
  • diode D3 and impedance inverter 30 are at the same time configured to approach an open circuit condition as the signal incident on the diode approaches a given upper amplitude threshold. As the amplitude of the transmitted RF signal approaches the upper threshold, diode D3 increasingly clips the signal. By selecting a diode having the appropriate operating curve, it is thus possible to provide controlled attenuation of higher amplitude signals.
  • the magnitude of the signal received by the detection circuit has a linear correspondence to the transmitted RF signal.
  • diode D3 it is necessary to consider the effects of gain and attenuation on the detection signal prior when setting the reference voltage level(s) to be provided by reference level generator 22. This is believed to be within the level of skill of the ordinary artisan and a detailed description of the level setting process has therefore been omitted.
  • FIG. 3 A modified embodiment, which is especially suited for situations in which only relatively low transmit power levels will be encountered, is presented in FIG. 3.
  • the load terminal of coupler 12 is shunted, providing a short circuit to ground.
  • such a termination permits the largest amount of power to be reflected back towards the detector circuit is thus particularly useful where relatively weak, low amplitude transmission is contemplated. Since this arrangement does not discriminate between high and low amplitude signals, however, larger amplitude signals would also be reflected, presenting the possibility of damage to the detector circuit and other components at higher output levels.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Transmitters (AREA)
  • Control Of Amplification And Gain Control (AREA)
EP96301903A 1995-03-31 1996-03-20 Circuit pour détecter le niveau de puissance d'émission à caractéristique améliorée Withdrawn EP0735670A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US414668 1989-10-03
US08/414,668 US5678209A (en) 1995-03-31 1995-03-31 Transmit power level detection circuit with enhanced gain characteristics

Publications (2)

Publication Number Publication Date
EP0735670A2 true EP0735670A2 (fr) 1996-10-02
EP0735670A3 EP0735670A3 (fr) 1998-04-22

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP96301903A Withdrawn EP0735670A3 (fr) 1995-03-31 1996-03-20 Circuit pour détecter le niveau de puissance d'émission à caractéristique améliorée

Country Status (8)

Country Link
US (1) US5678209A (fr)
EP (1) EP0735670A3 (fr)
JP (1) JPH08288771A (fr)
KR (1) KR960036392A (fr)
CA (1) CA2170667A1 (fr)
MX (1) MX9601183A (fr)
SG (1) SG67912A1 (fr)
TW (1) TW296504B (fr)

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SE506168C2 (sv) * 1996-01-17 1997-11-17 Allgon Ab Sätt och anordning för mätning av reflektionsförlusten hos en radiofrekvent signal
JP3093638B2 (ja) * 1996-06-18 2000-10-03 埼玉日本電気株式会社 出力レベル制御回路
US6148220A (en) * 1997-04-25 2000-11-14 Triquint Semiconductor, Inc. Battery life extending technique for mobile wireless applications
US5956627A (en) * 1997-07-08 1999-09-21 Uniden San Diego Research & Development Center, Inc. Temperature compensated power control circuit
US6236271B1 (en) * 1997-09-30 2001-05-22 Conexant Systems, Inc. Multi-layer carrier module for power amplifier systems within a digital cellular telephone
US6442378B1 (en) 1998-07-15 2002-08-27 Avaya Technology Corp Power level determination device in an RF booster for wireless communications
JP2001217663A (ja) * 2000-02-02 2001-08-10 Nec Saitama Ltd 送信回路
JP3885922B2 (ja) * 2000-03-07 2007-02-28 株式会社ルネサステクノロジ 半導体チップとそれを用いたｉｃカード及びｒｆｉｄ
US7190935B2 (en) * 2001-09-14 2007-03-13 Rf Micro Devices, Inc. Amplifier power detection circuitry
US7010284B2 (en) 2002-11-06 2006-03-07 Triquint Semiconductor, Inc. Wireless communications device including power detector circuit coupled to sample signal at interior node of amplifier
US20040072554A1 (en) * 2002-10-15 2004-04-15 Triquint Semiconductor, Inc. Automatic-bias amplifier circuit
US7228114B2 (en) * 2003-05-21 2007-06-05 Harris Stratex Networks Operating Corporation Wide dynamic range power detection scheme
US7418244B2 (en) 2003-08-04 2008-08-26 Analog Devices, Inc. Radio transmitter with accurate power control
US7177370B2 (en) 2003-12-17 2007-02-13 Triquint Semiconductor, Inc. Method and architecture for dual-mode linear and saturated power amplifier operation
US7693491B2 (en) * 2004-11-30 2010-04-06 Broadcom Corporation Method and system for transmitter output power compensation
US20060280261A1 (en) * 2005-06-10 2006-12-14 M/A-Com Eurotec Bv. System and method for controlling power output from a power amplifier
US7440731B2 (en) * 2005-07-27 2008-10-21 Freescale Semiconductor, Inc. Power amplifier with VSWR detection and correction feature
US8032096B2 (en) * 2006-09-29 2011-10-04 Broadcom Corporation Method and system for compensating for antenna pulling
US8391811B2 (en) * 2009-12-30 2013-03-05 Triquint Semiconductor, Inc. Input-power overload-protection circuit
KR101119910B1 (ko) * 2010-05-03 2012-02-29 한국과학기술원 모바일 ｒｆｉｄ 리더 송수신 시스템
TW201228431A (en) * 2010-12-28 2012-07-01 Acer Inc Mobile communication device and adjusting method thereof
US11177837B1 (en) * 2020-06-12 2021-11-16 Apple Inc. Duplexer with impedance inverters
US20220302935A1 (en) * 2021-03-18 2022-09-22 Skyworks Solutions, Inc. Power amplifier systems with non-linear antenna impedance for load compensation

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EP0503718A1 (fr) * 1991-03-11 1992-09-16 Philips Electronics Uk Limited Amplificateur de puissance et appareil de transmission incluant un tel amplificateur de puissance
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Also Published As

Publication number Publication date
MX9601183A (es) 1997-02-28
SG67912A1 (en) 1999-10-19
JPH08288771A (ja) 1996-11-01
EP0735670A3 (fr) 1998-04-22
CA2170667A1 (fr) 1996-10-01
US5678209A (en) 1997-10-14
KR960036392A (ko) 1996-10-28
TW296504B (fr) 1997-01-21

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